1. Field of the Invention
The present invention relates to a wafer dividing method that separates a wafer into individual devices along streets as separation lines formed in the wafer.
2. Related Art
Conventionally, a wafer on the surface of which a plurality of devices such as ICs, LSIs and the like are formed is separated into individual devices, using a dicing apparatus or the like, that are widely used in a variety of electronic devices. Then, in an effort to make electronic devices compact and lightweight, prior to separation into individual devices the wafer is placed upside down and secured on a holding table of a grinding apparatus and its rear surface side is ground so as to give the wafer a thickness of, for example, 20-100 μm (see, for example, JP-A-2004-319885).
However, a wafer formed thin by grinding bends like paper, which makes such a wafer both difficult to handle in later processing steps as well as easy to damage. Consequently, the applicant has proposed a technology that involves grinding only that portion which corresponds to a device area so as to form a recessed portion in the rear surface side of the wafer, and forming on the outer periphery of the wafer an annular reinforcement part having a thickness that is the same as before grinding (JP-A-2005-165395).
However, when locating the streets formed on the front surface of the wafer and dividing the wafer into individual devices by cutting them out from the front surface side, it is necessary to affix dicing tape to the rear surface side of the wafer and fix it to a dicing frame to the outermost periphery of which dicing tape is affixed, which creates a difference in height between the outer periphery margin and the recessed portion in the rear surface side of the wafer. As a result, in order to absorb that difference in height at the dicing tape, the dicing tape must be formed to a special shape and ordinary dicing tape cannot be used. Therefore, although it is desirable to affix dicing tape to the rear surface side of the wafer and support it with the dicing frame and cut along the streets from the rear surface side so as to divide the wafer into devices, after the wafer is divided into devices, it is necessary to push the devices with a pin from the rear surface side of the devices so as to pick up the devices from the dicing tape. As a result, ultimately, it is necessary to affix dicing tape to the rear surface side of the wafer.